1. Field of the Invention
The present invention relates to an advanced configuration and power interface (ACPI) compliant computer system and overtemperature protection method therefor and, more particularly, to an ACPI compliant computer system and overtemperature protection method therefor in which the system automatically enters a “sleep” state complying with the ACPI specification when an inner temperature of the system exceeds a predetermined temperature.
2. Related Art
A computer system, particularly a portable computer, generally has many hardware devices incorporated in a small space. Accordingly, if the computer system is operated in an “on” state for a long time, an inner temperature thereof may be increased. As a result, the operation or function of easily heated or thermally sensitive devices, such as a central processing unit (CPU), may be adversely affected.
To prevent the easily heated devices from being damaged, it is necessary that the inner temperature of the system not exceed a predetermined temperature value. For this reason, various methods have been provided, for example, a method of driving fans, a method of decreasing clock frequency of the CPU, etc. However, these methods have a limit when it comes to reducing the inner temperature of the system. Accordingly, there has been developed a computer system which employs a technique for preventing the inner temperature from exceeding a predetermined value by entering a “sleep” or “suspend” state when the inner temperature of the system exceeds the predetermined value.
An example of a computer system which adopts the latter technique is a computer system using a known system management technique, such as an advanced power management (APM) technique. In a computer system which uses the APM technique, management of heat or temperature, as well as the APM, is implemented by basic input-output system (BIOS) instructions stored in a read-only memory (ROM). For example, when a request to transition from an “on” state to a “sleep” or “suspend” state due to an excess of inner temperature of the system occurs, the BIOS receives notice of the request via an operating system transparent interrupt known as a system management interrupt (SMI). Upon occurrence of such a request, the BIOS communicates the request to the operating system which, after notifying all operating system level device drivers, generates an SMI returning control to the BIOS. It is the responsibility of the BIOS to manipulate the computer system to enter the “sleep” state after performing a “save to disk” operation or the like, which causes a hard disk drive or the like to store the present status of the system. On wake-up, the BIOS again receives notice via an SMI, and restores date stored in the hard disk drive or the like before returning control to the operating system. Thus, in the computer system using APM, there is no problem in entering the “sleep” state in the case of an excessive inner temperature, and in restoring data stored in the hard disk or the like upon wake-up, since all actions are performed by the BIOS only.
However, when the technique for preventing excessive inner temperature is used in a computer system employing the newer ACPI jointly developed by Intel, Microsoft and Toshiba, a problem occurs. Namely, when a power management or configuration event occurs, the operating system is notified via an operating system visible interrupt, known as a system control interrupt (SCI). It is the operating system itself that directs all system and device power state transitions, and data storing and restoring, relative thereto. However, it is still the responsibility of the BIOS to manipulate the necessary software state information, and to control the necessary hardware to perform the requested action when a request relative to heat or temperature occurs, for example, when the inner temperature of the system exceeds the predetermined value. Also, the ACPI uses a new “sleep” type, S3 or S4, instead of the “save to disk” mode or the like used in the APM. When the “sleep” type S3 is executed, processor and cache context are lost, but hardware maintains memory and some processor configuration context. When the “sleep” type S4 is executed, the hardware has powered off all devices, although platform context is maintained. Thus, even though the BIOS still controls the computer system to enter the “sleep” state after performing the “save to disk” operation and the like in the presence of an excessive inner temperature, the operating system recognizes that the computer system must resume in the “sleep” type S3 or S4 upon wake-up. Therefore, the operating system does not correctly restore data stored by means of the BIOS, and a problem results in that the system is halted.